[size=150][center]How do you do this problem:

"Find the sum of the arithmetic series."

"13+20+27+ ... +272"

Yours,

Highly Confused!!![/center][/size]

"Find the sum of the arithmetic series."

"13+20+27+ ... +272"

Yours,

Highly Confused!!![/center][/size]

Guest Apr 25, 2012

#1**0 **

[input]sum ( 13+x*7, x=0..((272-13)/7) )[/input]

this is your series:

13+20+27+ ... +272

this is the series in reversed order:

272+265+258...+13

the sum of one element of the series and one element of the reversed series (at the same index) is always the same:

13+272=285

20+265=285

27+258=285

... = 285

you have (272-13)/7 +1 =**38** such terms.

then the sum of 2 times the arithmetic series is: 38 * 285 =**10830**

the sum of the arithmetic series "13+20+27+ ... +272" is then: 10830/ 2 =**5415**

KatieeeBethhh16:"13+20+27+ ... +272"

[input]sum ( 13+x*7, x=0..((272-13)/7) )[/input]

this is your series:

13+20+27+ ... +272

this is the series in reversed order:

272+265+258...+13

the sum of one element of the series and one element of the reversed series (at the same index) is always the same:

13+272=285

20+265=285

27+258=285

... = 285

you have (272-13)/7 +1 =

then the sum of 2 times the arithmetic series is: 38 * 285 =

the sum of the arithmetic series "13+20+27+ ... +272" is then: 10830/ 2 =

admin
Apr 25, 2012